A DISCUSSION TO MODEL EXOTHERMIC REACTIONS AND IRREVERSIBLE VARIATIONS OF ELECTRICAL CONDUCTIVITY

Jean RIVENC (1), Richard PERRAUD (2), Gilles PERES(1), Thierry ZINK(3), David

ANDISSAC(3), Richard MILLS(4), Jacques CINQUIN(2)

(1) Airbus Group Innovations, Toulouse, France

(2) Airbus Group Innovations, Suresnes, France

(3) Airbus Operations SAS, Toulouse, France

(4) Airbus Operations Ldt, Filton, UK

ConfidentialOUTLINE

• CONTEXT AND OBJECTIVES

• SIMULATION OF EXOTHERMIC REACTION WITH

COMSOL

• SIMULATION OF IRREVERSIBLE VARIATION OF

CONDUCTIVITY

• RESULTS

• FEEDBACK

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ConfidentialSTUDY CONTEXT

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• A350: first aircraft in Airbus with composite fuselage.• Incidental contact between cable and composite structure (e.g. chaffing);• Current Icc into composite.

Composite structureIcc

Equipment

Network

voltage

Zinstallation

Fastener

Current return

structure

Zreturn

Design of a safe aircraft installation + protection devices => short-circuit has no consequence.

Comsol Conference Munich - Oct 13th 2016 - J Rivenc et al

ConfidentialOBJECTIVES

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Tomorrow:•New composite materials;•Different installations;•Different protection devices (circuit breakers, solid-state…)•Different voltages (e.g. 540VDC);

Limitation of physical tests (repeatability, cost, duration)

⇒ Numerical tool for predicting the damage;

Damage = f (composite, aircraft installation)

Size

Shape

Plies sequence

Plies and interplies thickness

Thermal parameters

Electrical parameters

Voltage (DC, AC, PWM)

Network impedances

Breakers tripping time

Comsol Conference Munich - Oct 13th 2016 - J Rivenc et al

ConfidentialPHENOMENA TO SIMULATE

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• Strong coupling between Electric and Thermal;

• Carbon fibers anisotropy;

• Exothermic thermo-oxidation of resin;

• Irreversible variation of electrical conductivity;

• Influence of circuit impedance and generator regulation.

=> Comsol Multiphysics

ConfidentialSIMULATION OF EXOTHERMIC REACTIONSimulation with Comsol

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• Resin thermo-oxidation is exothermic (DSC / TGA measurements);• Heat transfer in solid / Phase change = problem: temperature rise

decreases !!! => simulated phenomenon is endothermic.

ConfidentialSIMULATION OF EXOTHERMIC REACTIONSolution

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Temperature rise increases !!! => Exothermic reaction => OK.

ConfidentialSIMULATION OF IRREVERSIBLE VARIATION OF

ELECTRICAL CONDUCTIVITY

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Confidential

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RESULTSCorrelation between tests and simulation

16V

126A

MODELLINGEXPERIMENT

Comsol Conference Munich - Oct 13th 2016 - J Rivenc et al

t=600 ms

Confidential

Comsol Conference Munich - Oct 13th 2016 - J Rivenc et al

RESULTSExample of mass loss mapping

ConfidentialFEEDBACK

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☺• Computation of the damage, with the various multiphysics phenomena

with Comsol Multiphysics => Target achieved !

• No possibility to simulate exothermic phenomena with « Heat transferwith phase change » => need to « create » a local power densityfunction;

• Long computing times: 24 to 48h for a problem with xxxx numbers of freedom (workstation: multicores processor Intel ® Xeon ® CPU E5-1650 v3@3.5 GHz, 128 GB RAM , OS Windows 7, 64 bits)

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ConfidentialACKNOWLEDGMENT

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The authors are very grateful to the Comsol support team in France for valuable technical discussions, and especially to Mr Fabio Bocchi.

Merci !

Comsol Conference Munich - Oct 13th 2016 - J Rivenc et al